Buellia disciformis (Fr.) Mudd

Man. Brit. Lich.: 216, 1861. Basionym: Lecidea parasema var. disciformis Fr. - Nov. Sched. Crit., 8: 9, 1826.
Synonyms: Buellia major De Not.; Buellia major f. crustulata A. Massal.; Buellia parasema (Ach.) De Not.; Hafellia disciformis (Fr.) Marbach & H. Mayrhofer
Distribution: N - VG, Frl, Ven (Lazzarin 2000b, Nascimbene 2008c), TAA (Nascimbene & al. 2006e, 2007b, 2008c, Nimis & al. 2015), Lomb, Piem (Caniglia & al. 1992, Isocrono & al. 2004, 2006), VA (Valcuvia 2000, Valcuvia & al. 2000b), Emil (Fariselli & al. 2020), Lig (Putortì & al. 1999b, Giordani & Incerti 2008). C - Tosc (Loppi & al. 1999a, Putortì & Loppi 1999b, Loppi & Putortì 2001), Umb (Ravera 1998, Ravera & al. 2006), Laz (Bartoli & al. 1997, Ravera 2002, Massari & Ravera 2002), Abr (Caporale & al. 2016), Mol (Caporale & al. 2008, Genovesi & Ravera 2014, Caporale & Ravera 2020), Sar (Loi & al. 2000, Zedda 2002). S - Camp (Garofalo & al. 1999, 2010, Aprile & al. 2003, 2003b, Nimis & Tretiach 2004, Blasi & al. 2010, Brunialti & al. 2013, Ravera & Brunialti 2013), Pugl (Nimis & Tretiach 1999), Bas (Bartoli & Puntillo 1998, Ravera & al. 2021c), Cal (Puntillo 1996, Incerti & Nimis 2006), Si (Stofer 2006).
Description: Thallus crustose, episubstratic or rarely endosubstratic, continuous to rimose-areolate, thin to moderately thick, pale white to greenish grey, dull, smooth, epruinose, sometimes delimited by a dark prothallus. Apothecia lecideine, 0.3-1.5 mm across, with a black, flat to rarely convex, epruinose disc, and a thick, persistent, raised proper margin. Medulla I-. Proper exciple of radially arranged hyphae, darker brown in outer part, paler within, extending from the deep reddish brown hypothecium; epithecium brown, N-; hymenium colourless, 70-90(-100) µm high, strongly inspersed with oil droplets; paraphyses simple to moderately branched in upper part, the apical cells swollen, with a brown pigment cap; hypothecium brown. Asci 8-spored, clavate, Bacidia-type. Ascospores 1-septate, but sometimes with 2 additional false septa, soon brown, narrowly ellipsoid with pointed, paler ends, sometimes slightly curved, (12-)17-25(-30) x (5.5-)7-10(-13) µm, the wall thickened subapically, but not at septum, not ornamented. Pycnidia rare, black, globose, unilocular. Conidia bacilliform, straight, .5-9 x 0.7-1 μm. Photobiont chlorococcoid. Spot tests: K+ yellow, then sometimes brownish, C-, KC-, P- or P+ faintly yellow, UV-. Chemistry: atranorin, plus traces of fulgidin and fulgoicin.
Note: a holarctic, humid subtropical to southern boreal-montane lichen found on smooth bark in rather humid woodlands, especially in open beech forests of the montane belt. Some forms with pluriseptate spores from coastal Tyrrhenian Italy perhaps deserve further study: they might prove to belong to a distinct taxon, corresponding to Lecidea parasema sensu De Not., which has a different chemistry (Giralt & al. 2000). The species is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c).
Growth form: Crustose
Substrata: bark
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

Commonnes-rarity: (info)

Alpine belt: absent
Subalpine belt: extremely rare
Oromediterranean belt: absent
Montane belt: rather rare
Submediterranean belt: extremely rare
Padanian area: absent
Humid submediterranean belt: very rare
Humid mediterranean belt: extremely rare
Dry mediterranean belt: absent

pH of the substrata:


Solar irradiation:








Altitudinal distribution:


Predictive model
Herbarium samples

Leif Stridvall - Source: http://www.stridvall.se/la/galleries.php (Courtesy: Anita Stridvall)

P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (13316)

Pier Luigi Nimis CC BY-SA 4.0
Herbarium: TSB 9232